"Human beings are bizarre when they see somebody off the telly. I'm going to write a book on the ways people recognise you while pretending not to. It's very weird - and, until it happens to you, you can't conceive of it. But, in the end, it gets very tiring. You can talk to 70 people in one day. They come and say, `Can I touch your hair?' It's the difficulty of always being observed. The days when you're feeling vulnerable are the hardest because you're still being looked at. I was aware that if I shouted at my child in the street, people would say, `Oh, she's just like her character'."
The punters were a doddle, however, compared to Fleet Street's finest. "I once went on holiday to Italy with some female friends, and there was a photographer's long lens on me in the swimming-pool. They obviously had nothing better to do. You can't quite comprehend it. It's as if you're reading about someone else. They bring your private life into what's happening to your character in EastEnders.
"People become so familiar with you. In the greengrocer's recently, a woman called me Carol, and I had to say, `My name's not Carol. My name's Lindsey. I'm an actress and EastEnders isn't real.' Every now and then you want to claim your name back. I want to be known as Lindsey Coulson rather than Carol Jackson."
Now you can see why she chose to leave Albert Square for the slightly less high-profile surroundings of Out of Hours, a new BBC1 medical drama about doctors who are on call during the night and the weekend. Coulson has swapped Carol's scraped-back hair, jeans, T-shirts and dangly jewellery for the business-like hairdo, neat tartan skirt, white coat and stethoscope of Dr Cathy Harding. She is professionalism personified as she copes calmly with, say, a wedding party who have food poisoning after the groom's ex-wife did the catering.
"I thought, `You may never work again', but instinctively I felt that it was the right time to leave EastEnders," says Coulson. "I thought I'd explored all the possibilities with Carol. I'd cried myself out. And there were so many more characters I wanted to play. But I didn't want to move straight on to another working-class woman. It was important that the new character had no children or dog. I just had to be the still listener, rather than the person dishing out the emotional stuff. In the beginning on Out of Hours, I found that difficult. I thought, `Hang on, I do the emotion. Here comes boring Cathy Harding.' But you realise you can't go around as a doctor crying all the time. Cathy actually has good social skills. She takes you as a whole person. To her patients, she says, `This isn't just a headache. It's a headache because of this'."
Coulson was a hairdresser for six years, before studying acting at Mountview. She went on to appear in such works as an experimental production of Hamlet, in which she played a 33-weeks pregnant Ophelia. "It was fairly controversial," she laughs. "There was a possibility that it was either Polonius's or Laertes's child, but the real explanation was that I was pregnant and still wanted to work."
The big break came nine months after her daughter was born, when Coulson landed the part of Carol. "I did worry that I might be typecast," she concedes. "But it's because of EastEnders that I'm where I am today. I got to play some wonderful stuff." The moving scenes when her son, Billy, was kidnapped, or when her daughter, Bianca, had to have an abortion linger long in the mind.
Coulson used to receive letters from women in situations similar to Carol's, asking her to sort out their lives - "It was like counselling." She reckons Carol struck such a chord because "she was fundamentally honest, and didn't get anything in life easily. Everything she'd got, she'd fought for." Coulson wouldn't rule out a return to Albert Square. "Never say never, as Sean Connery puts it. Now, I wouldn't mind his career - or money."
There are even some aspects of Carol Jackson that Coulson admits to missing. "Now I have to be angry at home," she confesses. "I used to get it all out at work."
`Out of Hours' begins on Wednesday on BBC1 at 9.30pmReuse content